Metal Roofing Corrison

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_ Corrosion is the bane of all metal building products and yet the standard measure of corrosion resistance is still most commonly the neutral salt spray test (ASTM B-117) that virtually everyone concedes is a very poor indicator of field performance. However, the industry has years of data gathering experience with salt spray, and so there is strong tendency to stay with what you know, even when you know it isn’t ideal. It is worth remembering that the original purpose of the salt spray test was to monitor product performance consistency, not to predict years of field performance. The best measure of field performance is, of course, actually monitoring buildings over many years under many different field conditions, but this has the practical disadvantage of requiring decades of monitoring.
___ Realizing this situation, a group of companies involved throughout the value chain of metal building and roofing manufacture worked together over the past decade to construct and inspect a series of building roofs with the goal of determining which roofing features lead to the highest degree of corrosion. Armed with this information, could these features be combined to construct a panel test rack that would accelerate natural field corrosion to a more manageable time frame, say less than five years?
In 2000 and 2005 U. S. Steel, Henkel, AkzoNobel, Precoat, and Morton Buildings cooperated to build a series of metal buildings in different locations around the US using well characterized GALVALUME™ coated steel sheet, chrome-containing and chrome-free pretreatments, chrome-containing and chrome-free paints, and coil coating processes. A series of different pretreatments, primers, and topcoats were coil-applied and buildings erected in the Northeast, Southeast, and Midwest of the US. This allowed real life corrosion characterization of different painted metal systems to be evaluated. The pretreatment-paint systems included both commercial and experimental products at the time. The systems also included both hexavalent chromium-containing systems as well as chromium-free systems. Additionally, these materials were put in outdoor exposure testing at the Battelle site in Daytona Beach, Florida at 120 feet from the ocean as well as in neutral salt spray and cyclic accelerated corrosion testing. This would allow future comparison of all the test methods.rlw3-2
___ It was also important to have buildings in different geographical locations, as corrosion mechanisms are different depending on the local environment of temperature, humidity, acid rain, etc. The focus of the building inspection was the roof, and specifically the lap and drip edges of metal roof. Typical corrosion levels can be seen in Fig. 1, where the drip edge (top) shows slight corrosion starting and the lap edge (bottom) shows some white rust stain on the side of the major rib and red rust and water under the lap edge.
___ One of the difficulties in defining the best conditions to test painted metal performance is that optimal test conditions depend on what is to be learned. To measure paint chalk and fade, it is best to have vertical edges and scribes using a high slope. However in the present corrosion study, the more informative system turned out to be lap edges and drip edges with a low slope. When all the buildings were inspected the generalizations listed below could be drawn.
1. The north side of the roof shows more corrosion than the south side.
2. Lower slope shows more corrosion than higher slope.
3. Sheltered edges that spend more time in the shade show more corrosion than sunny edges.
4. Lap edges show more corrosion than drip edges.
___ The common feature of all these observations is that the locations which remain wet longer show more corrosion. This can be due to slower water runoff when there is low slope or slower water drying due to shade or less wind, or capillary action holding water under a lap edge. It was noteworthy that the corrosion tendencies after 6-11 years exposure were more dependent on the location and four conditions listed above than on the actual pretreatment and paint system. Thus, the degree of corrosion was more dependent on the conditions the roof experienced than on the different chemistries being employed. These observations led to the following design features in constructing a test panel rack to mimic these conditions.
1. Panel design. Assemble a pair of panels so that both a drip edge and a lap edge are available for rating the extent of corrosion.
2. Low slope. The rack is designed with a low 10° slope.
3. Sun/wind shelter. Panels are sheltered from all direct sun and most wind by placing the rack against a north facing wall with additional wind protection from the prevailing westerly wind.
4. Rain shelter. Panels are placed on lower levels of the rack so that a covering roof layer reduces any direct rinsing action of rainfall. This will increase the exposure to naturally occurring atmospheric corrosives and minimize rinse-off by rain.
This test and rack have been referred to as the Sheltered Exposure Roof Corrosion (SERC) test. A test panel rack incorporating all these features was built and installed on the roof of the Henkel facility in southeastern Michigan (Figure 2). The first rack was built with four levels of polypropylene pegboard for attachment of the panels, leaving room for a roof over the top shelf so that the fourth level could also hold test panels. The rack was installed adjacent to a north facing wall and sheltered to the west by another wall extending above the roof section on which it was placed. The rooftop location also meant that uncontrolled road salt would not be scattered on the rack, which could otherwise happen with ground level installation during Michigan winters.
The test panel design was also optimized to use a single standard 4″ x 12″ panel which was cut into a 2 ½” x 12″ and a 1 ½” x 12″ piece. These two pieces then present a freshly cut lap edge as well as a drip edge when fastened together in an overlapping fashion. The two panel pieces are taped together on three sides to ensure they remain tightly layered, as overlapping roofing panels would, and they are then attached to the pegboard shelves of the test rack with all plastic fittings to avoid initiating any galvanic corrosion. The panel pair is held slightly off the test rack surface to avoid any random capillary effects under the bottom of the panel pair and the drip edge. Figure 3 (top) shows a schematic of the panel attachment to the rack and (bottom) a photograph of a typical assembled test panel attached to the test rack.

A variety of test panels have been on the Henkel test rack since June 2012. On the rack we are currently comparing a matrix of substrates (CRS, HDG, GALVAUME™ coated steel sheet and Aluminum) and pretreatments (Cr(VI), Cr(III), and non-Cr) with a standard coating of primer and paint. Precoat has built a similar SERC test rack for comparing products from their coil coating lines. Figure 4 shows a series of test panels of hot dipped galvanized (HDG) coated with a variety of pretreatments under a chrome-containing primer and a siliconized polyester topcoat. The panels photographed in Figure 4 had only been on the test rack for 18 months, and after this short time did not show any measurable difference between the Cr(VI), Cr(III), and non-Cr pretreatments.
___ The next steps in this cooperative effort between all five companies are to perform a follow-up building inspection and correlate the results with Florida exposure panels, standard lab salt spray and cyclic corrosion tests, and the new SERC test rack panels. Now that the buildings are 9 and 14 years old, this second building inspection three years after the first inspection will let us determine if the corrosion trends seen earlier continue or whether new corrosion tendencies are noticed. After the 6 and 11 year inspection, the specific location on the roof was more important in determining the extent of corrosion than was the actual selection of pretreatment or paint system. This meant that the combination of factors that defined the SERC test (remaining wet longer) were more important than the actual pretreatment-paint system employed on the metal. However, it is possible that after three years longer in the field, the pretreatment-paint systems will start to differentiate themselves more. Secondly, a data comparison of building exposure and the various accelerated tests versus the SERC test will let us see how effectively they correlate with observed building exposure or other tests. The SERC test panels will only have two years of outdoor exposure, so it may be too early to see demonstrable differences. However, any indication at this early date would be very promising as it would show the value of an outdoor test rack to better predict real life corrosion in a more reasonable 2-3 year time frame.

 

 

EQ Coatings

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Why an Interest in EQ Coatings?
___The Steel Industry is a highly competitive world market. The industry is always in search of innovative and fresh manufacturing methods to improve quality and lower costs. One wouldn’t automatically think the metal stud industry utilizes cutting edge technology to create their products, since studs are well hidden and only visible during construction, but this is a common misconception. Progression in the engineering of stud design and stud manufacturing processes has followed a challenging path similar to that of the more well-known automotive industry. Throughout the years, the automotive industry has seen the approval of countless regulatory guidelines, pressuring automotive manufacturers to become innovative in their processing, leading to the creation of better operational processes, new metallurgical steels, new technology development in roll forming and stamping methods, plus the creation of new coatings to provide better corrosion resistance and impart specific characteristics, such as weldability and improved formability. Just as these regulatory guidelines pushed automotive manufacturers to innovate, the metal stud manufacturers were driven by the need to remain competitive against alternative building materials (eg. wood and concrete). Metal studs are sold and priced by the pound, so the need to be market competitive added pressure for stud manufacturers to engineer innovative designs and processes that drive out costs while creating products that are equal to or superior to the products already available. These innovations can be seen through many advancements; one such example being the creation of special tooling that imparts specifically designed shapes and ridges which work to improve strength (yields) while reducing both gauge and weight.
___When the discussion turns to materials, metal stud manufacturers primarily utilize galvanized substrates. These materials have worked well for manufacturers as zinc premiums have been stable over the past several years. However, in 2014 and 2015, experts project that zinc premiums will drastically increase. As the gauges of the metal studs are reduced, a correlation can be observed where the percentage of reduction in the thickness of the metal studs increases the percentage of zinc to the overall metal stud thickness and therefore increases the zinc premiums. These higher zinc premiums have also contributed to pressuring stud manufacturers to innovate, leading to some metal stud manufacturers taking advantage of purchasing excess automotive, high quality Galvanneal substrates and subjecting those substrates through the process of cold-reduction in order to drive yields up while obtaining equal strength from light gauges. The creation of new processing techniques such as this one led to the design and creation of coatings that were specifically formulated for the metal stud industry and are best known as EQ Coatings. EQ Coatings have been shown to significantly outperform standard metallic coatings such as:
• G40/G60/G90 Hot-Dip Galvanizing and A40/A60 Galvanneal
• 60G/60G, 90G/90G Electro-Galvanized
• GF20/GF30/GF45 Galfan
___EQ Coatings were developed to provide equivalent or superior corrosion protection, compared to approved metallic coatings that are listed in the ASTM A1003 standard for metal studs. While the “EQ” stands for Equivalent, EQ Coating manufacturers and test data insist that EQ Coatings are nothing short of being superior coatings.

Interior Drywall Steel Stud Framing – Codes and Standards
___Over the past several years, there have been countless discussions between metal stud manufacturers and metal stud industry associations over the acceptance of EQ studs and whether or not EQ Coatings conform to industry standards. Some regulating bodies have dealt with these discussions for several years, mostly due to the confusion caused by the distribution of misinformation in the marketplace. The SFIA (Steel Framing Industry Association) Technical Director Pat Ford explained in a recent Webinar, co-sponsored by the SFIA and AWCI associations, that EQ Coatings conform to the many codes within IBC, ASTM, AISI and ICC. Though there are many ASTM standards associated with manufacturing and specifying Cold Formed Members (metal studs), the key standards that are applicable to EQ Coatings are:
• ASTM C645; Per Section 4.2:
Members shall have a protective coating conforming to Specification A653 – G 40 minimum or have a protective coating with an equivalent corrosion resistance.
(Note that this “equivalent” provision has been in the standard for over 20 years.)
• ASTM A1003; per sections 9.1.3 for Metallic Coated Sheet Steels;
9.1.3.1; No more than 10% loss of coating… at the end of the prescribed test duration.
9.1.3.2; Minimum exposure for type NS steels is 75 h.
• ASTM A1004; per section 6.2 Procedures for Metallic Coated Products;
6.2.1: Use Practice ASTM B-117 (Accelerated Salt Spray Test) to evaluate corrosion conformance…
These standards and requirements have been adopted into the SFIA QC program and serve as the basis for performance requirements for this program. In short, this program states, the requirements for a metallic G40 EQ (Equivalent) coating are:
• The manufacturer must show that the EQ coating is more than 50% metallic.
• It must submit to ASTM A1004 and ASTM B-117 Salt Spray tests per the listed protocols and sample quantities.
• It must pass the ASTM required 75 hour minimum test duration with less than 10% coating loss (i.e. – relative area of red rust)
In summary, for drywall framing, the IBC Code refers to ASTM standard C645 for guidelines. Relative to EQ Coatings, the other standards that reference guidelines for the performance are ASTM A1003, ASTM A1004 and ASTM B117.

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How do EQ Coatings Work?
___EQ Coatings are primarily (or entirely) composed of metallic compounds and are highly conductive. Due to their unique chemical nature, EQ Coatings require zinc, zinc alloy or zinc-iron alloy metallic coated base substrate to effectively work. EQ Coatings are Not Barrier Coatings, unlike more common coatings such as pretreatments, sealers, TFA’s (Thin-Film-Acrylics), primers and/or prepaints. EQ Coatings permanently (chemically and covalently) bond and integrate into the zinc, zinc alloy or zinc-iron alloy metallic coated substrate and become a singular composite coating system. It is this characteristic that provides the tremendous corrosion resistance properties. In some EQ Coating systems, cut edge and scratch resistance are so enhanced, compared to traditional standard metallic coated systems, that some EQ Coatings can provide self-healing characteristics.
___Typical G40 HDG or A40 Galvanneal metallic coated substrates are manufactured according to the ASTM A653 Standard for Galvanized Sheet Steel and are expected to have .40 oz./ft² (total for both sides) of coating weight (mass). The standard (A653) allows for a range in the galvanized coating weights but must have a minimum coating weight of .30 oz./ft² (total both sides). In closer review of the standard, the actual coating weight can be as low as .12 oz./ft² on a single side. The photo below shows the full coating weight range of a typical G40 HDG metallic coating that can be purchased from a steel mill and still be within the approved specification range. In review, the coating weights at the lower end of the G40 specification do not perform very well in an ASTM B177 salt spray test. Even coating weights at the high end of the G40 standard show 100% white rust at 48 – 75 hours.
___The galvanizing process can create vast valleys, fractures, pits and porosity in the zinc metallic surface. EQ Coatings are applied via a reverse roll coating application on a coil coating line and then cured with an IR or conventional oven. The combination of the coating and the process allows the EQ Coating to penetrate deep into the fractures and valleys within the zinc metallic coating, where it proceeds to chemically react with the zinc, sealing it off from the environment. It is this unique process and reaction that provides the tremendous corrosion protection associated with EQ Coatings. EQ Coating and a zinc metallic coating are more than just a basic coating. When combined, they become a singular permanent integrated composite coating. The unique level of corrosion protection provided by an EQ Coating allows metal stud manufacturers to utilize substrates that do not meet minimum metallic coating weight (mass) requirements of ASTM A1003 but when enhanced with a singular composite integrated EQ Coating system, they can provide extensive corrosion protection that meets or exceeds the corrosion expectations associated with the metallic coating weight ranges referenced above.

rlw2-3Superior Performance of EQ Coatings
___As mentioned earlier, EQ Coatings were specifically designed and created for the metal stud industry. They were designed to be applied to excess automotive Galvanneal, HDG or Electro-Galvanized, be cold-reduced by 20% to 50% after coating, slit down and then roll-formed into finished metal studs. EQ Coatings have been shown to outperform other mill applied or other post applied coatings. Some EQ Coatings are formulated to provide superior cut-edge and scratch protection. In the photo, the flat test panels on the top show cut edge and scribe performance, as compared to the G40 control pictured at the bottom.
EQ Coating formulations can be modified to meet the needs of many specialized requirements or applications, such as:
• Hexavalent Chromium Product
• Trivalent Chromium Product (RoHS Compliant)
• Chrome-Free Product (RoHS Compliant)
• Lubricity (to aid in the roll forming and stamping applications by improving productivity, increasing tool life and reducing the level of wet lubricants used – translating to cost savings for the customer)
• Tints that can be added for desired appearance or product recognition

 

 

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Other Advantages of EQ Coatings
___In accordance with the ASTM A1003 Standard; 9.1.1 Not all coatings will react the same under a given set of environmental conditions. These minimum coating designations assume normal exposure conditions and construction practices. When more severe exposure conditions are probable (for example: in coastal areas), consideration should be given to specify heavier coating weights (mass).” In this section of the ASTM A1003, the standard recommends specifying substrates with better corrosion performance when in severe environments, such as G60 or G90 HDG. EQ Coatings can easily accommodate this requirement at a fraction of the cost, compared to zinc premiums on substrates above G40.Since September of 2011, when Eco-Green Coatings, a division of Chemcoaters, developed their EQ Coating known by the trade name as InterCoat®ChemGuard, there have been over 500 million linear feet of EQ coated studs sold in the marketplace without a single claim for corrosion in the field.
Other steel product industry segments have found an interest and have accepted the EQ coatings due to their field performance, as depicted in the data above, and the tremendous corrosion resistance. Some of these applications include:
• Transportation; one large vehicle manufacturer has specified InterCoat®ChemGuard into the floor of their vehicles. They now offer a 10-year warranty over the traditional 5-year warranty for corrosion protection.
• Service Centers are specifying InterCoat®ChemGuard to eliminate transient rust when coils are shipped from the Midwest to Mexico.
• Major U.S. Appliance manufacturers are testing InterCoat®ChemGuard to improve corrosion issues in dishwashers and laundry applications.
• Major HVAC manufacturer utilizes InterCoat®ChemGuard as a hybrid primer for roof-top units to improve corrosion protection.
• Major U.S. steel door manufacturer is testing InterCoat®ChemGuard to improve corrosion and reduce field corrosion claims.
• Major U.S. steel mill is currently running InterCoat® ChemGuard trials to replace hexavalent chromium chemtreatment with a RoHS compliant trivalent non-hazardous InterCoat®ChemGuard 300 coating and still gets the same corrosion (or better) than the hexavalent chromium Chemtreat.

 

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 Innovation and Change
___It is important for steel driven industries to continue to innovate and stay ahead of the competition provided by alternative materials. The Automotive industry is faced with aluminum and carbon composites competition. The Appliance and HVAC industries are utilizing more plastics. The Building & Construction industry has wood, concrete and composite products to compete against. Many of the EQ Coating manufacturers and applicators service all of the various steel industries. The synergies that exist between all of these steel markets produce unique opportunities for technology advancements, such as EQ Coatings, to service multiple industries rather than a single market. It is advancements like this that will ultimately lead to driving down costs and allow steel products to remain competitive among these vast and diverse marketplaces. Despite some resistance to change, the quality and performance of these innovative coatings are clearly defined in the ASTM standards that have been in place for over a decade and that is because these standards were written to accommodate innovation in coating technologies and provide defined test methods to insure adequate levels of performance for the application.

 

Flatness Demand Keeps Steel Firm Busy

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Leveling equipment has helped a Midwestern steel service center company take its business to the next level.
The company is McNeilus Steel, a family-owned firm that dates back to the 1940s. After beginning as a scrap yard, McNeilus moved into new steel, then added coil processing and grew more from there. Today, the business includes three service centers and a fabrication facility, as well as the scrap yard.
___ McNeilus operates out of three locations in the Upper Midwest. The corporate office is part of a 700,000 sq. ft. facility in Dodge, MN. The other facilities are a 500,000 sq. ft. plant in Fargo, ND, and the company’s newest addition, a 220,000 sq. ft. plant in Fond du Lac, WI.
Like other service center operators, McNeilus has been navigating through rough economic waters. The company’s success in these tough times can be attributed in part to equipment upgrades that have helped it meet the demands of sheet metal fabricators who have become more sophisticated about the steel they purchase.
___ “Our customers want better product to help them with their processes. They want steel that’s free of surface defects and coil memory,” reports Greg Head, general manager of the firm’s Wisconsin facility. “The goal is to create a consistently flat sheet product that our customers can be confident their processes will be consistent.”

Leveling Lines On the Job
___ One piece of steel-enhancing equipment now installed at all McNeilus service centers is a stretcher leveler. The firm opted for stretcher levelers because of customer demand for “the flattest product they can get without memory of being in a coil,” Head notes.
As the name suggests, a stretcher leveler eliminates coil memory by stretching coiled steel to produce extremely flat sheets. According to Head, this is important to the many customers who are now cutting steel with lasers. “When applying heat to material sitting on a laser bed, the material must be flat and remain flat,” he says. The reason, he explains, is that material flexing can cause problems with the laser heads, which often operate on unmanned production lines.
Down the production line, parts may go through other processes such as forming. Head points out that stress-free material from the stretcher leveler is key to the production of consistently formed parts that meet specifications.
___ McNeilus has purchased a total of four stretcher levelers in the last 11 years. In 2003, the company’s first stretcher leveler was installed at its Minnesota headquarters, as was the second two years later. The firm’s North Dakota plant got the third in 2010, and the fourth was recently installed at the Wisconsin facility. “Once we installed our first stretcher leveler, we recognized the value and benefits of the machine, so we continued to add them,” Head notes.
All four units were purchased from Illinois-based Red Bud Industries. “Our thinking was that if we were to continue adding these leveling lines, we wanted to purchase what we felt was the best,” Head says. “We think we’ve done that.”
___ The four RBI stretcher levelers can handle steel ranging from 20 gauge on the light side up to 5/8″-thick, 60″-wide material on the heavy side. Normally, material thicker than 5/8″ is in plate form already and so does not need to go through a stretcher leveler, Head explains, adding that McNeilus supplies but does not process larger product of this kind.

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Products and Markets
___ Stretcher levelers have given McNeilus a boost in its efforts to serve a number of markets that require flat sheets. These include agriculture, energy, manufacturing, and commercial construction. Steel from McNeilus leveling lines can be found in a variety of products, including trailers, grain wagons, cement trucks, lawn mowers, skid loaders, military vehicles, and wind towers.
___ Stairs and other wind tower components are part of the company’s healthy energy industry business. “We might not produce pipe that transports oil, but we produce the material used to build many other things that are part of the energy infrastructure,” Head says.
___ An added benefit for McNeilus is that activity in the energy sector trickles down to many other markets. For example, Head says, “people need to move dirt and other material in conjunction with the energy business.” With the energy industry booming in North Dakota, he adds, there is a “tremendous amount” of this trickle-down activity in that area—activity that in some cases requires metal products from the McNeilus plant in North Dakota.
___ In addition to North Dakota, McNeilus mainly serves customers in South Dakota, Minnesota, Wisconsin, and Iowa. The company also does some business in Canada.
___ At McNeilus facilities, workers are on the job 24/7, taking orders during the day and loading trucks at night. The company owns and operates a fleet of more than 100 vehicles that deliver material on a daily basis. “We can handle just-in-time service and many other types of delivery programs customers require,” Head says.
___ As for the newly installed line he oversees, Head claims it has given a boost to both corporate efficiency and sales. “We are close to our primary coil mills which cuts freight costs by eliminating four hours’ travel between here and Minnesota. So the new line enables us to be more competitive as well as opening up some new doors for us.”